🧬 Pigeonpea — Genetics and Breeding

Pigeonpea improvement has moved from varietal selection to globally significant hybrid breeding breakthroughs. This lesson covers mating behavior, male sterility systems, and the disease-pest priorities of Indian breeding.

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Origin and Importance

Pigeonpea (Cajanus cajan (L.) Millsp., 2n = 22) belongs to the family Fabaceae and is the only cultivated species in the genus Cajanus. Its centre of origin is India, which is also the largest producer, accounting for about 90% of global output. Pigeonpea is a protein-rich pulse (20-22% protein) and an important component of rainfed cropping systems due to its deep root system and ability to fix atmospheric nitrogen through symbiosis with Rhizobium.

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Reproductive Biology

Pigeonpea is considered often cross-pollinated with natural outcrossing ranging from 5 to 40% depending on insect activity. The flowers are papilionaceous and exhibit a tripping mechanism. This intermediate mating system allows breeders to use both pure-line selection and hybrid breeding approaches.

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Male Sterility and Hybrid Breeding

The development of the world's first commercial pigeonpea hybrid was a significant achievement of ICRISAT. Three types of male sterility have been exploited:

• Genetic male sterility (GMS) — controlled by a single recessive gene (ms). Hybrid ICPH 8 was developed using GMS but had seed production challenges due to 50:50 fertile-to-sterile ratio.
• Cytoplasmic-genetic male sterility (CGMS) — derived from the wild relative Cajanus cajanifolius (A4 cytoplasm). This is the preferred system for large-scale hybrid seed production.
• Temperature-sensitive male sterility (TGMS) — useful in certain environments but not yet commercially deployed.

The landmark hybrid ICPH 2671 (2010) was the world's first CGMS-based pigeonpea hybrid, showing 30-40% yield advantage over the best varieties. It was followed by ICPH 2740 and ICPH 3762.

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Breeding Objectives

1. High grain yield — determinate and semi-determinate plant types for mechanical harvesting.
2. Fusarium wilt resistance — caused by Fusarium udum, the most destructive soil-borne disease. Resistant varieties include Asha (ICPL 87119) and Maruti (ICP 8863).
3. Sterility mosaic disease (SMD) resistance — transmitted by the eriophyid mite Aceria cajani.
4. Pod borer resistance — Helicoverpa armigera is the key pest; wild relatives like C. scarabaeoides offer resistance genes.
5. Short duration — extra-early types (90-120 days) like ICPL 88039 and Pusa 992 for rice-fallow and relay cropping systems.
6. Photo-thermo insensitivity — enables adaptation across latitudes and seasons.

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Summary Cheat Sheet

Quick Recall Points\n- Pigeonpea is often cross-pollinated with variable natural outcrossing.\n- Commercial scaling shifted from GMS to CGMS (A4 cytoplasm).\n- Core resistance traits: Fusarium wilt, sterility mosaic, and pod borer tolerance.\n\n### Exam Traps\n- ICPH 8 was early and important but had seed production constraints.\n- Hybrid advantage depends on robust seed production ecology, not only field performance.

References

2 sources • [1] [2]

[1]

ICAR eCourse: GPBR 213 Crop Improvement-I (Kharif Crops)

Book

[2]

ICAR Crop-specific research bulletins (IIRR, IIMR, IIMR Sorghum, ICRISAT, CICR, SBI, CRIJAF)

Website